A large proportion of the population in Côte Ivoire lives in rural
areas, often in isolated homesteads that are difficult to supply with grid electricity.
Only 30% of the localities have access to electricity. Furthermore, household
connections do not keep growing, thus the absolute proportion of the population
without electricity is increasing. The supply of power to rural area is not
economically viable because of the exorbitantly high cost of distribution and
associated transmission loss. Transmission losses were estimated to 23% in 2007
(Koffi and Koman, 2008). Many electric utilities suffer
from poor reliability. As an alternative, one may think of auto-generator power.
Auto-generator entails establishing standalone electric power generation at
the village and/or building level. Local electrification approaches to produce
energy services with a quality compatible to grid electricity were: diesel generator,
photovoltaic system, photovoltaic-diesel hybrid system (Schmid
and Hoffmann, 2004).
One of the main objectives of the development policy is also to encourage the
use of renewable energy sources. Renewable energy technologies, such as photovoltaic
one, can offer flexible small scale solution matching the energy needs of rural
population (Shafie and Abdelaziz, 2011; Dimas
et al., 2011; Khatib, 2010; Schmid
and Hoffmann, 2004).
Many studies show that photovoltaic power systems will have an important share
in electricity in the future (Dincer, 2011; Carrion
et al., 2008).
The electricity from PV can be used for a wide range of applications, from
power supplies for small consumer products to large power stations feeding electricity
into grid. Many studies in recent years are developed in grid-connected PV systems
(Erge, 2001; Celik, 2006; Kim
et al., 2009).
In Nigeria, a study that compared PV, diesel and grid extension found that
PV has a remarkable potential as a cost effective option for low power electrical
energy supply to the rural communities in the country (Oparaku,
2003). In another study in Brazil, it has been shown that it was more economic
to convert diesel systems up to 50 kW peak power into PV/diesel hybrid systems
(Schmid and Hoffmann, 2004). In Thailand, it was concluded
in a study that compared diesel generator with PV system and line extension,
that PV/diesel hybrid system with 75% of the load supplied by diesel provided
the lowest electricity production cost (Boonbumroong et
al., 2004). In an economical comparison of diesel and photovoltaic water
pumping system in Namaqualand, South Africa, it has been shown that diesel water
pumping systems could be considerably more expensive than PV systems in the
long run, if life cycle costing is used as the basis for comparison (Matlapeng
et al., 2006).
Research to date has arrived at various conclusions due to costs used for different times (thus the impact of inflation on purchase of equipment, fuel and labour were ignored) and at different locations (thus studies were based on different insolation levels). This study makes an economic comparison between photovoltaic, diesel generator and grid extension. The purpose of the study was to analyze which technology is more cost effective suitable to use in rural areas by simulation. For all the systems, the initial costs and the life cycle costs were determined. The parameters used for simulation were load energy demand and grid extension distance.
MATERIALS AND METHODS
Solar energy resources in côte dIvoire: Côte Ivoire
lies within a tropical region and hence has a tropical climate. The country
has two main distinct seasons: the rainy season (from March to August) and the
dry season (from November to March). The other months are the boundaries of
the two seasons.
The temperatures throughout the year respectively range from a minimum average
of 22°C to a maximum average of 32°C. The average experiences between
5 and 8 sunshine hours per day. This gives an annual average solar insulation
of about 5.0 kWh m-2 day-1 with a peak of sunshine being
received between March and April, according to regions and the SODEXAM (national
meteorological office) (Sako et al., 2007; Andoh
et al., 2007).
Systems design and operation: The following set of technical was considered:
||Decentralized photovoltaic system alone, consisting of photovoltaic
modules, batteries and inverter, able to supply the energy demand
||Diesel generator plus energy storage using batteries and inverter, so
that the generator will only be operated at full load during the necessary
hours to supply the daily energy requirements
The sizes of the photovoltaic system components (arrays, batteries and inverter)
were determined using the peak sun hour method. To calculate the size of the
PV panel needed by using that method, the load demand per day and solar energy
availability for site have to be determined (Dimas et
al., 2011; Chancelier and Laurent, 1995). The
average insolation value of 4 kWh m-2 day-1 was used.
The efficiency factors of losses in battery and inverter were estimated to be
0.8 and 0.85, respectively. Three days of battery storage were considered to
compensate low insolation and cloudiness. The maximum depth of discharge of
battery was assumed to be 0.7. The diesel generator capacity was calculated
from the total load demand. The generator is operated daily at a duty cycle
of 5 h per day.
Economic analysis: The life cycle cost calculation used is the present worth technique in which the present worth values of the capital, maintenance, repair and energy costs have been determined. The repair and replacement costs of the system include the costs of replacing solar batteries every five year. Equipment prices were obtained from local suppliers. The costs of the grid extension and energy were obtained from the National Electric Company. Time horizon considered was of 30 years corresponding to the expected life of photovoltaic panels. The interest rate and the inflation rate considered were respectively 10 and 4%. An exchange rate of 500 was used to convert the costs in local currency to US$. Regarding the diesel generator operation, a specific consumption of 0.4 l kWh-1 was adopted.
Data analysis: Sensitivity analysis was performed using variation in load demand and grid extension distance. For all the systems the life cycle costs over 30 years life cycle are considered. Technical and economic factors are examined by simulation using Microsoft Excel.
RESULTS AND DISCUSSION
The life cycle costs of diesel generator and Photovoltaic (PV) system have been compared to determine the conditions under which either technology is more cost effective for the same energy demand.
The capital and operating costs for diesel generator and photovoltaic system
are laid out over 30 years in Fig. 1. A major distinction
between the two technologies is shown in this graph. Diesel generator has a
relatively low initial capital cost and a significantly higher maintenance and
operating cost. The photovoltaic system has a large initial capital cost and
a negligible operating cost. These results are in concordance with those of
Oparaku (2003) and those of Schmid
and Hoffmann (2004).
Since the photovoltaic system has no moving parts, it has minimal maintenance and no fuel costs. The graph shows that the photovoltaic system has a lower life cycle cost.
Sensitivity analysis was performed to determine how the costs will vary with charges in load demand and grid extension distance. Figure 2 shows the results of the economic comparison model. The relative cost of grid extension versus photovoltaic system is calculated over a 30 year photovoltaic system life. The PV/grid cost ratio is established by rating the cost for PV system installation and generation and the cost of grid extension and generation. The PV/grid ratio is plotted against the distance between the grid tie point and the site using the load energy demand variable.
When the PV/grid ratio is less than one, PV is a more economical alternative. The graph shows that PV system is more cost-effective than the grid extension when the load is less than 10 kWh per day. From 10 to 50 kWh day-1, the site must be at least 3 to 5 km away from the grid point.
||Diesel versus PV (Load demand: 3 kWh day-1)
||PV versus Grid extension varying distance from Grid and daily
Figure 3 shows the cumulative costs for PV vs Diesel and Grid extension. The life cycle costs were calculated over 30 years period taking into account upfront costs, operating costs, maintenance costs and replacement costs. The Grid extension distance considered was 1 km. The daily energy requirement was assumed to be 3 kWh day-1.
PV system has a low cumulative cost when compared to Grid extension. In this case PV is more cost effective than Grid. As previously stated, PV has a high upfront capital cost but low maintenance cost compared to Diesel. The breakeven point of PV system with Diesel generator is 6 years while that of Grid is 15 years. Grid extension has the highest upfront capital cost. When the daily demand rises to 15 kWh day-1 for the same grid extension distance (Fig. 4), Grid becomes more cost effective than the others after 5 years. The breakeven point of PV system with Diesel generator decreases to 5 years.
Compared to Diesel, PV is more cost effective for long period. Grid extension
costs are both distance and daily energy demand dependant. This assessment is
in well concordance with Oparaku (2003) results.
The critical factors in comparing Grid to PV system are the size of the daily
energy requirement and the grid extension distance. The present value costs
of Grid versus PV are shown in Fig. 5 for differing load demand
sizes and Grid extension distances.
||PV versus Diesel and Grid, daily energy demand: 3 kWh day-1,
load distance from Grid: 1 km
||PV versus Diesel and Grid, daily energy demand: 15 kWh day-1,
load distance from Grid: 1 km
||PV versus Grid for different load demand sizes and grid extension
PV is the most cost effective source compared to Grid in the area below the
curve. This graph can be used to predict which of PV and Grid is more economically
suitable to use in remote site.
This study proves that diesel generator can be considerably more expensive than PV system in long term (up to 6 years) because of the high operating cost of diesel generator. The difficulties of purchasing imported spare parts and fuel and the requirement of skilled labor to keep it running make diesel generator a non realistic alternative solution for remote sites.
Compared to grid, PV cost effectiveness is both daily load demand and distance to grid dependant. Over 5 kWh day-1 load demand, the distance to grid must be at least 1 kilometer. Over 50 kWh day-1 load demand the grid extension distance must be up to 6 km.
As we project into the future, the price of PV is surely to come down while the price of petroleum products is likely to go up. This can lead to a reduction in the years to breakeven. It has also been proved that PV systems are an environment friendly source of energy and what must also be taken into consideration.